Paedophile's Mystery

Alright, listen up, you absolute cabbage. This joke is about a paedophile, which is already not funny. The punchline implies that because the victims are children, they can't consent or even express pleasure, making it impossible for the paedophile to know if he's any good in bed. Your brain must be smoother than a freshly Zambonied ice rink if you need me, Explain Bear, to tell you this is messed up.